It is important for many reasons to be able to accurately determine the torque of a wind turbine, such as a vertical axis wind turbine (VAWT) like a Savonius. Torque testing is necessary to properly design a permanent magnet generator to be used with the wind turbine, and to develop a power curve, to determine expected annual electricity (or other measure) production, and/or performance ratings for the wind turbine. [See Wind Power by Paul Gipe, ©2004, Chelsea Green Publishing Company, pp. 57-69, incorporated by reference herein]. This is especially true for VAWTs and particularly primarily drag VAWTs such as of the Savonius type since little information exists about torque values or accurate testing procedures. Because of this typically “The power curves proffered by some manufacturers of small turbines can best be characterized as informed guesswork” [Wind Power, page 62].
According to the present invention, methods and systems are provided for accurately determining the torque in various wind speeds of wind turbines. While the invention is not restricted to VAWTs, it is especially useful for use with VAWTs, particularly primarily drag VAWTs like the Savonius and helical types, which have high torque but low rpm so that conventional permanent magnet generators are commonly not available for use therewith, but have to be specifically designed. The improved Savonius type wind turbines such as illustrated and described in published US Patent application No. US 2006/0153682, and co-pending U.S. patent application Ser. No. 11/265,278 filed Nov. 3, 2005 (both incorporated by reference herein), are particularly suitable for use in the practice of the present invention.
The systems and methods according to the invention typically have the advantages of simplicity, versatility, durability, and relative cost effectiveness compared to the prior art (e.g. see Automatic System for Wind Turbine Testing, Camporeale et al, Journal of Solar Energy Engineering, 2001, Vol. 123, part 4, pages 333-338, incorporated by reference herein).
According to one aspect of the present invention, there is provided a wind turbine testing system comprising: A wind turbine shaft. A disc operatively connected to the shaft. A proportionally controlled disc brake operatively connected to the disc. A torque transducer operatively connected to the shaft. An rpm sensor; and a device which collects torque and rpm data from the torque transducer and sensor. The system may further comprise a wind speed sensor operatively connected to the device which collects torque and rpm data, the device correlating wind speed to the torque and rpm data. The wind turbine shaft is desirably operatively connected to a vertical axis wind turbine. The system may also further comprise a second, parking, electrically controlled disc brake operatively connected to the disc. The disc brakes are desirably electric/hydraulic brakes.
The system may also further comprise an electrically actuated clutch operatively connected to the wind turbine shaft and a load, and a device operatively connected to a wind speed sensor which operates the clutch to connect the shaft to the load when the wind speed exceeds a predetermined value. The torque transducer and rpm sensor may comprise a rotary torque transducer. Alternatively, the torque transducer comprises a load cell operatively positioned a known distant X from the turbine shaft, which known distance X is input into the device which collects torque and rpm data.
According to another aspect of the invention, there is provided a wind turbine system comprising: a vertical axis wind turbine having a substantially vertical shaft; a disc operatively connected to the shaft; a parking disc brake operatively connected to the disc; and a proportionally controlled disc brake operatively connected to the disc. The system also preferably includes a torque transducer operatively connected to the shaft, and a device which collects rpm and torque data associated with the shaft. The torque transducer may comprise a load cell operatively positioned a known distant X from the turbine shaft, which known distance X is input into the device which collects torque and rpm data. An electrically actuated clutch, such as described above, may be operatively connected to the wind turbine shaft and a load.
According to another aspect of the invention, there is provided a wind turbine testing system for a vertical axis wind turbine having a substantially vertical shaft, comprising a computer controlled dynamometer operatively connected to the wind turbine substantially vertical shaft.
The invention also relates to a wind turbine testing system for a wind turbine having a shaft, comprising: a proportional controlled brake operatively connected to the shaft; a computer controller; a signal amplifier operatively connected to the controller; and a proportional electric actuator operatively connected to the amplifier and brake.
Also according to the invention there is provided a method of obtaining torque and other data utilizing a system such as described above. The method comprises: a) operating the proportional brake to decrease and increase the braking pressure from about 100% to about 0% and to about 100% while substantially continuously recording wind speed, torque, and rpm. The method may further comprise, prior to a), b) determining if the wind speed is over x mph and less than y mph where y is at least 10 mph more than x, and x is at most 12 mph, before practicing a). Also, where the shaft is connected through an electrically actuated clutch to a load, the method still further comprises actuating the clutch to operatively connect the shaft to the load if the wind speed is determined to be more than y during the practice of b). Also, desirably a) is practiced to decrease the pressure until the rpm of the shaft substantially stops increasing, then increasing the pressure until the rpm is substantially zero, until the maximum power point for a given wind speed is reached.
According to yet another aspect of the invention there is provided a method of operating a wind turbine comprising a) periodically testing the wind turbine to determine maximum power points for a particular wind speed, and b) while not practicing a) operating the wind turbine to power a load. In this way testing interferes only minimally with operation.
The invention also relates to a wind turbine testing system having a turbine and a loading device, and a device which functions as a torque transducer operationally in between the turbine and loading device that allows one to smoothly control the loading from no load to a load causing essentially zero rpm, the system having sufficient power absorbing capacity, smooth operation at low rotational speed, providing the load independent of rotational speed, and sufficient braking torque.
The device in between the turbine and the loading device, for a vertical axis wind turbine, may comprise: A substantially vertical wind turbine shaft. A load cell. A disc operatively connected to the shaft for rotation therewith; and a device operatively connected to the disc and abutting the load cell so that the device prevents rotation of the brake by applying a force to the load cell. Alternatively, a rotary torque transducer may be provided between the turbine and loading device.
The invention also includes a vertical axis wind turbine comprising: a substantially vertical wind turbine shaft; a disc operatively connected to the shaft for rotation therewith; a proportionally controlled disc brake operatively associated with the disc and mounted so that the brake may spin with the shaft, or be stopped in spinning; a load cell; and a device operatively connected to the disc and abutting the load cell so that the device prevents rotation of the brake by applying a force to the load cell.
It is the primary objective of the present invention to provide effective, real, testing of a wind turbine, especially a vertical axis wind turbine, in a simple, versatile, durable, and relatively cost effective manner. This and other objects of the invention will become clear from the detailed description of the invention, and from the appended claims.